Atmospheric Physics

This page lists all the PhD projects offered by Atmospheric Physics
group.

--Modelling the Terrestrial Atmosphere--

The Atmospheric Physics Laboratory has developed a comprehensive model
of the Earth's upper and middle atmospheres (15 km to 600km altitude).
This is being used for a number of studies, including comparisons with
satellite data, and ground-based instruments. One particularly important
strand of our work is the look at how effects in the lower atmosphere -
the troposphere where we have the weather and climate that affects us -
may be linked to what happens on the Sun or in near-Earth space. This
covers the fields of 'Space Weather', where, for example, we see how the
effects of solar flares can penetrate to the ground, and the way solar
variability might affect the climate.

In recent years evidence has
accumulated that there is a link between solar variability (in the sense
of changes in the solar cycle/sunspots and radiative output) and climate
change. This is controversial because the effects that are seen to
change cyclically on the Sun represent a tiny fraction of the Sun's
output, and most of the energy that reaches the Earth from the varying
phenomena is expected to be "soaked up" by the minute fraction of the
Earth's atmosphere that borders interplanetary space. However,
correlations show there appears to be linkage of some kind. A number of
theories have been developed to explain this, including some control of
clouds by cosmic rays, varying mechanisms for particle entry through the
Earth's magnetic shield, and the release of trapped wave energy from the
lower atmosphere by small modifications to the critical mesopause layer
of the atmosphere.

Apart from our own model studying these effects we have a collaboration
with the Met Office where we are looking at issues to do with coupling
their tropospheric model to our upper atmosphere model. One recent
project we have started is to look at how the 'Global Electric Circuit'
might affect the coupling to the magnetosphere and beyond. This Circuit
is driven by thunderstorms charging up the ionosphere above 100km height
to 250-300KV with respect to the ground. There is a "Fair Weather"
current back down from the ionosphere over the rest of the Earth. We are
trying to understand how this might affect the dynamics, chemistry and
thermodynamics of the atmosphere. Contacts: Prof. Alan Aylward (a.aylward AT ucl.ac.uk); Dr Anasuya Aruliah (a.aruliah AT ucl.ac.uk)

--Planetary Aurorae and Magnetosphere-Ionosphere Coupling--

The beautiful auroral displays of magnetised planets (such as the
Earth, Jupiter and Saturn) are the result of powerful global systems
of electrical current which flow between their ionospheres and
magnetospheres. At the giant planets, rapid rotation plays an
important role in the formation of auroral ovals. The Atmospheric
Physics Laboratory group at UCL have a wealth of experience in both
observations and modelling of the auroral physics and the global
atmospheric flows which arise via the electrodynamic coupling of the
planet and its space environment.
We have analysed enormous datasets of ground-based spectroscopic
observations of giant planetary aurorae, taken in infrared light,
which reveal the emissions from the ion H3+.
Such data have enabled us to confirm the primary role of this ion in
the heating and dynamics of the hydrogen-rich auroral regions of the
gas giants. Planned future work includes ongoing mapping of the
H3+ emissions in order to build a more
comprehensive picture of the physical conditions in the ionospheres of
the gas giants.

On the modelling side, we have built global models of the
thermospheres and ionospheres of Jupiter, Saturn and Uranus. These
have been used in pioneering studies of the effects of auroral
precipitation on upper atmospheric flows and planetwide heating
processes. Such studies are important for identifying the types of
energy inputs required to explain the unusually high temperatures in
the upper atmospheres. Planned future work includes more studies of
how time variability of the aurora and the magnetospheric conditions
affect the atmospheric flows and heating: a key question here is the
timescale associated with the atmosphere's response to changes in
magnetospheric conditions. We have recently collaborated with the team
who manage the magnetometer aboard the Cassini spacecraft on studies
of Saturn's magnetospheric structure, and we envisage that this
experience with spacecraft data will provide valuable future inputs
and constraints for our own planetary models.

--Magnetospheric Projects--

Since 2009, our 'Atmospheric Physics' group has extended our modelling expertise out into the magnetospheric region and constructed models of the disc-like, rapidly rotating magnetospheres of Jupiter and Saturn. We have published several studies comparing the Saturn model with observations from the Cassini spacecraft of the planet's magnetic field and plasma environment. Further comparative studies of this nature are needed. On the more theoretical side, we also wish to build a more 'complete' magnetospheric model for Saturn by including the effect of the solar wind interaction, which for example 'distorts' the planet's plasma sheet from an equatorial disc into a 'bowl-like' shape. Thus for someone interested in plasma / magnetospheric physics, there is a variety of options for postgraduate work.
Contacts: Dr Nick Achilleos
(nick AT apl.ucl.ac.uk);
Prof. Steve Miller
(s.miller AT ucl.ac.uk)

--Magnetospheric Turbulence at Saturn--

This project would suit a student
interested in the analysis of magnetic data from the Cassini spacecraft.
It focuses in particular on the nature of the fluctuations in the
magnetic field, how those fluctuations characterise different plasma
regimes in the magnetospher of Saturn, and in particular how the
spectrum of the fluctuations across different scales can give
information about turbulence in the system. The student would be working
closely with Dr. Patrick Guio and Dr. Nicholas Achilleos (nick AT apl.ucl.ac.uk), both of whom
have expertise in tools for this type of data analysis.

--Structure and Energetics of the high-latitude MIT system--

We have a network of Fabry-Perot Interferometers (FPIs) in
northern Scandinavia, within the Arctic Circle, used to study the
Earth's
upper atmosphere: the magnetosphere-ionosphere-thermosphere (MIT)
system.
This study is achieved by
measuring airglow and auroral emissions, more commonly known as the
Northern Lights. The upper atmosphere near the magnetic poles
is highly dynamic due to direct coupling with the turbulent solar
wind, via the Earth's magnetosphere. The project will involve
instrumental fieldwork with the FPIs, and collaboration with other
instruments such as the EISCAT radar and magnetometers, which provide
complementary observations of the ionosphere, as well as comparison
with the APL atmospheric model. The investigation will be into the
small-scale structure and the energetics of the interaction between
the neutral and charged particles of the upper atmosphere. Contact: Dr Anasuya Aruliah (a.aruliah AT ucl.ac.uk)

--Investigating the difference between satellite and ground magnetometer
measurements of the Earth's magnetic field--

The three Swarm satellites were launched by the European Space Agency last
November 2013. They will measure the Earth's magnetic field and its structure
to an unprecedented level of precision, Earth scientists and atmospheric
scientists will use the observations to separate out the magnetic field
generated by the Earth's core and mantle, from that generated by the ionosphere
and magnetosphere.
It has been discovered that the magnetic field measured by magnetometers on the
ground give different measurements from magnetometers on satellites. The aim of
the project is to identify the cause of this difference.
It is proposed that the altitude distribution of electric currents in the
ionosphere may be a primary source of difference. The UCL Coupled Middle
Atmosphere and Thermosphere model will be used to test the hypothesis. The
model simulations will be compared with magnetic measurements from the Swarm
satellite and ground magnetometers. Contact: Dr Anasuya Aruliah (a.aruliah AT ucl.ac.uk)

--Probing the Atmosphere of Jupiter and Saturn in the Far Infrared--

Probing the Atmosphere of Jupiter and Saturn in the Far Infrared
The wavelengths beyond 50 microns contain the spectroscopic signatures
of many molecules at temperatures and under environmental conditions
that cannot be easily accessed in other wavelength regions. These far
infrared wavelengths can only be observed using observatories placed
beyond the Earth's atmosphere as they are blocked from reaching the
ground even at the highest terrestrial observatories. One of the space
based observatories that UCL has been involved in building was the
European Space Agency's Infrared Space Observatory (ISO) which operated
from 1995 until 1998. Although almost all of the data from this
facility has now been published, significant and unique data sets taken
on the planetary atmospheres of Jupiter and Saturn have not see the
light of day. With the exciting new observations from the latest
infrared satellite (Herschel) now being released it is now time to
revisit the ISO observations and, together with the atmospheric
modelling expertise present in the Astronomy group, to build a new
detailed model of the planetary atmospheres of the gas giants to look in
detail at the chemistry and structure of their atmospheres and what
these unique data can reveal in conjunction with the latest
observations. Contacts: Prof Bruce Swinyard (bruce.swinyard@stfc.ac.uk) and Prof Steve Miller (s.miller@ucl.ac.uk)